Radio-isotope cameras using vacuum tubes with fiberoptic endwalls and luminiscent means of fiberoptic construction

ABSTRACT

This invention relates to cameras for visualization of internal organs and their pathology by means of radio-isotopes. The new devices are characterized by the novel combination of an image intensifying tube with a television pick-up tube and with means for rejecting the scattered gamma radiation. In addition the new cameras are provided with novel luminescent screens which are constructed of light conducting members of a tapered shape and phosphors mounted along the sidewalls of said members.

States tent Sheldon 51 March 6, 1973 [54] RADIO-ISOTOPE CAMERAS USING3,375,388 3/1968 Sheldon ..3l3/65 s VACUUM TUBES WITH FIBEROPTIC3,422,232 Z1329 Sheld0ln ..250/83v/38l3;lP 3,4 01 l 9 Stemg ass ..250 .3g gg gggg ggg ggggg B 3,021,834 2/1962 Sheldon ..250/213 VT CONSTRUCTION3,225,193 12/1965 Hilton et al ..250/71.5 s [76] Inventor: EdwardEmanuel Sheldon, 30 East P E A R B h It 40th Stre t, Ne Y k, N.Y. 10016e e w or AtrorneyPolachek & Saulsbury [22] Filed: Aug. 20, 1969 21 Appl.No.: 851,567 [57] ABSTRACT This invention relates to cameras forvisualization of 52 us. 01 ..250/71.5 s 250/77 250/83 3 R internalorgans and their Path1gY by means 5 1 isotopes. The new devices arecharacterized by the [51] Int Cl U Go 1/20 novel combination of an imageintensifying tube with [58] Field of Search 83 3 77 a television pick-uptube and with means for rejecting 80 i 5 6 the scattered gammaradiation. In addition the new cameras are provided with novelluminescent screens [56] References Cited which are constructed of lightconducting members of a tapered shape and phosphors mounted along theUNITED STATES PATENTS sidewalls of said members.

3,303,374 3/1967 Fyler ..250/80 13 Claims, 17 Drawing Figures PULSE 27a; 5 75 e8 28 g l c/pcu/r 1 g am /0c E U 2/ ours/a4 L cou urek RA-/$ar0/=E f5 SOURCE RADIO-ISOTOPE CAMERAS USING VACUUM TUBES WITHFIBEROPTIC ENDWALLS AND LUMINISCENT MEANS OF FIBEROP'IIC CONSTRUCTIONThis invention relates to Gamma Cameras which are also known asRadio-Isotope Cameras and has a common subject matter with copendingU.S. 3,499,017 filed Apr. 15, 1966 and issued Mar. 3, I970. Theaforesaid 3,499,107 was a division of U.S. 3,279,460 filed Dec. 4, 1961and issued Oct. 18, 1966, which was a copending division ofU.S.3,02l,834 filed Nov. 28, 1956, which has a common subject matter andwas copending with U.S. 2,877,368 filed Mar. 11, 1954. These devicesserve to produce visible images or patterns of the distribution of gammarays or other invisible radiations emitting isotopes in the examinedparts. Their primary use is in the medicine for diagnosis of malignanttumors in internal organs such as brain, liver, kidneys or pancreas.They are also useful in nondestructive testing in industry.

The present devices of this type suffer from lack of sensitivity whichrequires that the time of exposure to produce one picture may be as longas -30 minutes. Such long exposures cannot produce satisfactory imagesbecause patients obviously must breath and move during such long periodsof time. In addition such long exposures made impossible the study ofshort events occuring in the human body which are known also as dynamicstudies of body processes. The above shortcomings of the present art aregreatly improved by the novel devices to be described below.

It is therefore the purpose of the present invention to produce aRadio-lsotope Camera which has a much greater sensitivity than thestandard devices.

Another purpose of this invention is to produce a Radio-Isotope Camerasuitable for dynamic studies.

Another purpose of this invention is to make a device which will produceimages formed by radio-isotopes of a better definition and contrast thanthe present devices.

The novel devices are illustrated in the drawings as follows:

FIG. 1 represents the novel Radio-Isotope Camera system.

FIG. 1A to 1D represent modifications of the first imaging tube in thecamera system.

FIG. 2 represents a modification of the first tube which has a thininput endwall.

FIG. 2A represents a modification of the image tube with a thin endwall.

FIG. 3 represents a tube with electron multiplier plate.

FIG. 4 represents a novel luminescent screen using light conductingfibers for the Radio-Isotope Camera.

FIG. 4A-4F represent modifications of the novel luminescent screensusing light conducting fibers.

FIG. 4G represents a novel X-ray Cassette.

FIG. 1 shows the Radio-Isotope Camera system 1. The radio-isotope imageof the examined organ such as brain, or liver or kidney or pancreas isproduced by the emission of gamma rays. Radio-Isotope compound isselectively localized in the tumor or other pathological area 30 in thebrain 31 or other organ of the body. The emitted gamma rays get out ofthe skull, are collimated and focused by the collimating device 32. Thecollimated gamma rays beam impinges on the luminescent screen 3 or itsmodifications and is converted therein into an extremely weakluminescent image. The luminescent image is next transported to thephotocathode 7 of vacuum tube 2 and is converted into a beam ofphotoelectrons having the pattern of said radio-isotope emission. TheCamera 1 comprises a plurality of image tubes 2, 2a and 2b mounted in atandem together. The luminescent screen 3 may be mounted on the outsideof the input endwall 5 or may be mounted inside of the tube 2.

The input endwall 5 of the vacuum tube may comprise a fiberoptic part 6which comprises a plurality of light conducting fibers of a transparentmaterial of a high index of refraction, each of said fibers having anexternal part such as a coating of a material of a lower index ofrefraction than said fibers, which is described in detail in my U.S.Pat. Nos. 2,877,368 and 3,021,834. The input endwall 5 may be also of astandard type of glass endwall in which case the luminescent screen 3 ismounted outside of the tube 2 in a spaced relationship to said tube withan optical system disposed between them in order to focus theluminescent image from the screen 3 onto the photocathode 7.

In another modification shown in FIG. 2 the input endwall 6a is made ofa standard glass construction as distinguished from the fiberopticconstruction described above but has a novel construction in which thecentral portion 6b of said endwall is thinned out. This permits mountingof the luminescent screen 3 on the external surface of the endwall 6a ofthe tube 2 or its modifications without losing the resolution of theluminescent image which is unavoidable when the standard glass endwallis used. It is well known in the art that a thin endwall of the thinnessnecessary to preserve the resolution of an image in such device is notsufficient to support the atmospheric pressure. It was found howeverthat if the luminescent screen is of a single crystal or if a mosaic ofluminescent crystals is united together with a strong binder such assilicones or polycarbonates, the combined strength of such luminescentscreen 3 and of the very thin endwall 6b is sufficient to withstand theatmospheric pressure.

Also the novel fiberoptic luminescent screens 50, 63, and can be usedwith a thin endwall 6b and will prevent the breakdown of said endwall.This construction is shown in FIG. 2A.

The input endwall 6 or 6a may be of a similar diameter as the rest ofthe tube 2 or may be many times larger as it is shown in FIG. 1A. Thisconstruction permits the use of a large luminescent screen, which inmedical applications must be of diameter 6-9 inches, without the use ofoptical intervening means. The large size photoelectron image producedby the photocathode 7 may be demagnified electron-optically in the tube2 so that the remaining part of the tube 2 and other vacuum tubes in thecamera system 1 may be of a small size. It should be understood thatelectron-optical demagnification may be used for all vacuum tubesdescribed.

The vacuum tube 2 has a photoemissive photocathode 7 supported byendwall or the aluminum disc 23 or by mesh screen 24, as explained. Thephotocathode 7 may be of any photoemissive material but it was foundthat the best results are obtained with a photocathode of K-Cs-Sb,because it produces less dark current than other photocathodes such asof K- Na-CsnSb type.

The vacuum tube 2 is provided with a luminescent screen 10 mounted onthe inner surface of the opposite endwall 11. The screen 10 is providedwith a light reflecting and opaque layer 10a such as of aluminum whichis thin enough to be transparent to electrons. The endwall 11 comprisesa portion 12 made of light conducting members of the same type asdescribed above for the part 6 of the endwall 5. The construction ofluminescent screen mounted on the array of light conducting members isdescribed in detail in my U.S. Pat. No. 3,021,834.

The vacuum tube 2 and its modifications is provided also with focusingmeans 13 and electron accelerating means which are both connected to anoutside source of electrical potential.

The luminescent screen 3 and its modifications may be also mountedwithin the tube 2 and its modifications. If it is inside the vacuum tube2 it may be mounted on the inner surface of said input endwall for thesupport, as it is shown in FIG. 1B. In this embodiment the endwall 6cmay be of a standard glass construction. The luminescent screen isprovided with a light reflecting layer 3a. A light transparentseparating layer 70 is provided to prevent chemical interaction betweenthe photocathode 7 and screen 3. The layer 7a may be of A1 silicon oxideor of heat resistant plastics such as polycarbonates, sulphones orpolyamides.

The screen 3 may be also mounted in the tube 2 and its modifications ina spaced relationship to the endwall. In such case it needs a supportwhich may be in the form of an aluminum disc 23 as shown in FIG. 1C ormay be supported by an embedding layer of light transparent plastic suchas of polyesters, polycarbonates, sulphones or polyamides.

In some cases the luminescent screen 3 and its modifications may besupported by a light transparent plastic layer of one of aforesaidmaterials which is mounted on a supporting mesh screen 24 as shown inFIG. 1D. The luminescent screen 3 and its modifications may have aplanar or a curved configuration.

The tubes 2a and 2b have a similar construction as the tube 2, exceptthat they are provided with a higher electrical potential than the tube2 for further acceleration of electrons and intensification of the finalluminescent image. The tubes 2, 2a and 2b are mounted with theirfiberoptic endwalls in contact with each other. The combinedintensifying action of said plurality of tubes produces the fluorescentimage on the final luminescent screen in tube 2b which is 50,000 timesbrighter than the original luminescent image in the screen 3.

In some cases the vacuum tubes 2or 2a or 2b and their modifications maybe further provided with image intensifying plate 36 of electronmultiplying channelled type, as it is shown in FIG. 3.

It should be added that in some applications the construction of thispart of camera I may be modified so that instead of using 3 or morevacuum tubes 2, 2a and 2b as described above, a single vacuum tube isused. Such vacuum tube must be provided with a few intensifyingcomposite screens as it is described in my U.S.

I Pat. No. 2,555,423 and others.

The patient receives the necessary dose of radio isotope which emitsgamma rays or other invisible radiations. The radio-isotope isincorporated a vehicle which will localize preferentially in the part ofthe body which has to be investigated for example Technetium compoundscontaining "Tc localize well in the brain, whereas Selenium compoundscontaining "'Se are useful for pancreas and iodine compounds forthyroids. The amount of radio-isotope given to the patient has to bevery small because of patients safety. As a result of this limitationthe exposure to produce one image in the devices used at present has tolast 5-30 minutes. This as it was explained above causes inavoidablemotion and breathing defects in the final image. The present deviceproduces simultaneous amplification of the entire image by the factor of50,000 which allows to reduce the time of exposure and obtain picturesof much better resolution.

Another serious problem in producing the images of the organs of thebody by means of radio-isotopes is the. presence of scattered gammaradiation which being superimposed on the imaging gamma radiation actsas fog and destroys detail and contrast of images. The means forremoving at least a part of this fog are known as pulse amplitude orheight discriminating circuits. They are however truly effective only inthe gamma cameras of mechanical type in which the image is produced notsimultaneously but sequentially point after point and which resultsnecessarily in extremely long exposure as it was explained above. Thenovel system to accomplish the elimination of scattered radiation andpermit at the same time short exposures is shown in FIG. 1 and uses anovel combination of amplifying image tubes 2-2a-2b with a televisionpick-up tube of image dissector type 15 and with pulse amplitudediscriminating circuits 25. The vacuum tube 15 is provided with thephotocathode 17 of photoemissive type mounted on the endwall 16. Theendwall 16 should be made of light conducting members or comprising apart made of such light conducting members as it was described above forendwall 6 and its modifications. In some applications the endwall 16 maybe of standard type but in such case an optical system must beinterposed between the last image tube 2b and image dissector type 15which causes a great loss of light. The vacuum tube 15 is provided witha diaphragm 18 which has an aperture 18a which serves for the passage ofelectrons from the photocathode 17. In addition vacuum tube 15 haselectron focusing means and deflecting means 19 which may be of magnetictype or electrostatic type. The deflecting means serve to scan thephotoelectron beam from the photocathode 17 against the aperture 18apermitting the passage of only one image point at a given time. Thetransmitted electrons of each image point impinge sequentially on thesecondary electron multiplier 20 of a multistage type. The multipliedsecondary electrons are collected by the anode 21 and are converted intovideo signals over a suitable resistance as it is well known in thetelevision art. Video signals-corresponding to one image point at thetime are fed into pulse amplitude discriminating circuits 25. Thecircuits 25 serve to pass only video signals of a predetermined highamplitude and to reject pulses of a lower amplitude. In this way videosignals produced by the original imaging gamma radiation will be passedbut video signals produced by scattered radiation being of a lower energy than the original imaging radiation will be rejected. It may berepeated that the scattered gamma radiation corresponds to aphotographic fog in the sense that it does not contribute to the imagebut degrades and obscures the image. The original energy of gamma raysemitted by Neohydrine which is a radio-isotope of Hg and is useful fordiagnosis of brain tumors is about 289 KV. The scattered gamma radiationproduced by the collision of original gamma rays with brain tissues havea spectrum of different energies but all of them are below 289 KV andtherefore can be eliminated by the use of the circuits 25. In the samemanner "Technetium compounds which are also useful for brain tumorlocalization emits peak energy gamma rays of I50 KV whereas scatteredgamma rays are of a lower energy.

There are many types of pulse amplitude discriminating or analyzingcircuits which are well known in the art. Some of them are known asintegral discriminators and are described in detail in Chase, R.L.,Nuclear Pulse Spectrometry, McGraw-I-Iill, New York, 1961; Schmitt, 0.,A Thermionic trigger. J. Sci. Instr. 15, 24 (1938). Other morecomplicated types are known as Differential Amplitude Analyzers. Some ofthem are designed especially for stability and are described in detailin Kandiah, K., A sensitive pulse amplitude discriminator. Proc. Inst.Elec. Engrs. (London) Pt. II 101, No. 81, 239 (1954); Orvis, A. L.,Koenig, M. P., and Owen, C. A., Jr., In-vivo measurement of thyroidalradioiodine: effect of neck scatter. J. Clin. Endocrinol. Metab. 17, 966(1957). Even more advanced types are known as Multichannel Analyzers andserve for conversion of analog data into digital data, as it isdescribed in Scientific Literature. This technique is further developedby using means for storage of digital data as described in Hutchinson,G. W., and Scarrott, C. G., A high precision pulse height analyzer ofmoderately high speed, Phil. Mag. 42, 792 (1951). A thorough review ofvarious Discriminating Circuits is given in McCollom, K. E.,Discriminators, Nucleonics 17, No. 6, 72 (1959). It should be understoodthat all types of above described pulse amplitude analyzing anddiscriminating circuits and analog to digital conversion circuits may beused in my camera system 1.

In addition the camera 1 may use all image contrast in detail enhancingmeans such as image density tracers or quantizers.

The use of pulse amplitude discriminating circuits 25 is well known inthe art but none of the previous devices could use them and produce theresults which are possible only with the novel camera 1.

The novel Radio-Isotope Camera 1 is free from limitations of the presentdevices in which the spatial resolution is inherently related to theenergy resolution of the device excluding thereby the use ofradioisotopes of a low energy. The novel Radio-Isotope Camera 1 is freefrom limitations in the spatial resolu tion of other camera deviceswhich impaires the definition of the final image to be diagnosed.

The novel Camera permits also making pictures of examined organs in afew seconds time due to its much greater sensitivity.

The signals which passed Pulse Amplitude Discriminating Circuits may befed into display devices such as a kinescope 26 or an array ofluminescent diodes. The signals may be also fed into various storagedevices and/or in computers. The signals may be also fed into variousdata processing devices such as scalers, decimal registers, ratemeters,etc. It should be understood that all means for display or for storageor for counting or for other utilization of signals may be used in theCamera 1. The kinescope 26 may produce a luminescent image on itsluminescent screen 27, which may be photographed by a photographiccamera 28. The kinescope 26 may be provided with a fiberoptic endwall,as it is described in my U.S. Pat. No. 3,021,834.

The Camera 1 may also produce multi-color images using variousmulti-color display means which are known in the art.

One of the greatest problems in the present Radiolsotope Cameras is thebasic conflict between the sensitivity of said cameras and resolution ofimages. A good sensitivity of a camera requires a very thick luminescentscreen which will be capable of absorption of penetrating gamma rayssuch as KV gammas of Technetium or 289 KV of Hg or 364 KV of l. At thesame time the thicker is the luminescent screen the worse is theresolution of images produced by a gamma camera. It follows that thesetwo requirements are diametrically opposed to each other. This basicproblem was solved by the novel luminescent screens which use phosphorsin combination with light conducting members and which are described indetail below.

FIG. 4 shows the construction of one of such luminescent screens 50. Thescreen 50 is constructed of a plurality of light conducting members 51which are described in my U.S. Pat. No. 2,877,368 filed Mar. 11, 1954and in U.S. Pat. No. 3,021,834 filed November 1956 as follows:

The image conductor 51 consists of multiple fibers of material having ahigh refractive index such as quartz, rutile or special plastics. Inmany applications the image conductor must be flexible and easilymalleable. In such cases acrylic plastics such as Lucite or polystyrenesmay be used. Especially Lucite is suitable for this purpose because itcauses smaller losses of conducted light than other materials. Luciteand other above mentioned materials characterized by a high refractiveindex have the property of internal reflection of the light conducted bythem. Such materials cannot conduct a whole image as such but they canconduct well a light signal, it means an image point. The size of theimage point I found is determined by the diameter of a single conductingfiber 52. In my image conductor 1 assembled a bundle of such fiberswhich form a mosaic-like end-faces and which therefore can conductplurality of image points. All these image points will reproduce at theother end-face of the image conductor the original image provided thatthe image conducting fibers remain in their original spatialrelationship. Each fiber 52 should have, as was explained above, adiameter corresponding to the size of one image point. The

diameter of 0.1 millimeter is well suitable for the purposes of myinvention. In order to conduct an image of an area, e.g., of 1 squarecentimeter we must have many fibers 52, the number of fibers beingdependent on the resolution of reproduced image that we desire. If theresolution of the conducted image should be 4 lines per millimeter, andif the image is of one square centimeter in size, we will need 40 fibersof 0.25 millimeter in diameter. As in many examinations it is notpractical to be limited to the field of l cm?, I preferably use a fewhundred of such fibers combined in one image conductor, which will allowto transmit an image of a large area.

The light conducting fibers should be polished on their external surfacevery exactly. They may be also preferably coated with a very thin lightopaque layer which should have a lower index of refraction than thelight conducting fiber itself. Such coating may have a thickness of onlya few microns. I found a great improvement of flexibility of the lightconductor 51 can be obtained by having the light conducting fibers 52glued together only at their end-faces 51a and 51b. This is a veryimportant feature of my device because the main requirement from thelight conductor 51 is its flexibility and malleability. If the fibers 52are glued together along their entire length the flexibility andmalleability is so much reduced that it may be not possible to use it inmany examinations in which the walls or passages are fragile and may bedamaged by a rigid instrument. I found unexpectedly that having theconducting fibers 52 free along their path between the end-faces willnot cause any deterioration of the conducted image. I found that inspite of the fact that fibers between their end surfaces were freelymovable there was no blurring of the conducted image. It must beunderstood, however, that the fibers 52 at both end-faces of theconductor 51 must rigidly maintain their spatial relationship. Anotherimportant feature of this construction is that the diameter of the lightconductor 51 can be now increased because no space consuming binder orglue is present between the fibers 52 except at their end-faces. Insteadof using the binder at the end-faces of fibers 52, they may also be heldtogether at their end-faces by a fine mesh screen. Each fiber isthreaded through one opening of said mesh screen and is being held bysaid screen in constant position.

It may be added that smaller losses of light may be obtained if thefibers 52 are hollow inside instead of being solid.

The difference between the light conducting members 51 of the presentdevices and the light conducting members in the aforesaid parent patentsresides in a tapered which means conical construction of the lightconducting members 51. The core part or the internal part 52 of themembers 51 is of a transparent material of a high index of refractionsuch as quartz, rutile, glass or plastics as described above. Theexternal part or the coating part 53 is of material of a lower index ofrefraction than the part 52. The luminescent material 54 is mounted onthe sidewalls or adjacent to the sidewalls of the light conductingmembers 51. The luminescent material 54 may be of many phosphors whichare reactive to electromagnetic radiations or to atomic particles.Suitable phosphors are Nal (Tl), CsI, CaWO Ba(Pb)SO anthracene, uranylcompounds and others. In some cases luminescent glasses containing raremetals such as terbium, holmium or dysprosium or their compounds may beused also. One light conducting member 51 with the luminescent layers54a and 54b represents one image point of the examined part of the body.The length of the members 51 was found to have no effect on resolutionand on the size of an image point. This novel feature permits the use ofa phosphor layer 54a and 54b of a great length which means of a greatthickness without any damage to resolution of images. It may be recalledthat in the present luminescent screens their thickness has to be verysmall because the resolution of two-dimensional images produced by suchscreens is limited to the thickness of the luminescent layer itself. Itmay be repeated that the radio-isotopes emit very energetic rays such asof ISOKV-SOOKV energy. Such gamma rays cannot be absorbed by theconventional luminescent screens because a luminescent layer of thethickness between 1 inch and 4 inch is required for this purpose. Suchthickness will produce an image point of 1-5 inch size which isobviously useless for producing any images. On the other hand the novelluminescent screen 50 or its modifications to be described below can useluminescent layers 54a and 54b of the thickness 1-4 inch withoutimpairing resolution of image.

In addition it was found that the novel screen 50 or its modificationscan produce such results not only when using phosphors transparent totheir luminescent emission such as Nal(Tl) or CaWO but unexpectedly theymay also use layers of phosphors such as Csl, Ba(Pb)SO or ZnSCdS whichare nontransparent. In distinction to the standard screens in which suchnontransparent luminescent layers are limited to the thickness of afraction of one millimeter, as the luminescent radiation cannot escapefrom them otherwise, the novel screens can use such layers in thethickness of many inches.

The use of very thick layers of phosphors was made possible by the noveldevice in which the luminescent layers are combined with the lightconducting members 51 which are provided with a conical configuration.The luminescent light from phosphor 54a and 54b enters the'members 51through their sidewalls and is trapped and transported along saidmembers by internal reflection mechanism until it exits through theoutput endface 51a.

If transparent phosphors are used the light conducting members 51 shouldbe separated from each other by light opaque means 56 to prevent anoptical crosstalk between adjacent light conducting members. In somecase light opaque means 56 may be used only between every second lightconducting member 51. If the phosphors used are of non-transparent type,the light opaque means 56 may be omitted.

It was found that the greater is the tapering of the light conductingfibers 51, the better is their efficiency of the light transfer.

Further increase in sensitivity of luminescent screen 50 and itsmodifications may be obtained by applying an additional phosphor layer58 to the input endfaces 51b of the members 51 or to the entire inputside of the screen 50, as it is shown in FIG. 4A.

The light conducting members 51 carrying the luminescent layers on theirsidewalls are united by binders of organic type such as silicones or ofinorganic type such as solder glasses, potassium silicates or ceramics.In some applications instead of using the binders, the endfaces of lightconducting fibers 51 are preferably held together at their endfaces by amesh screen 60 and 61 as it is shown in FIG. 4B which illustrates thenovel luminescent screen 63. Light conducting fibers 51 are threadedthrough openings 62 and 62a of said mesh screens 60 and 61 and are heldby said screens in constant position.

The luminescent material 54 may be injected in a liquid form orinsufflated in a powder form or deposited in a crystal form into thespace between the sidewalls of the adjacent two light conducting members51. The openings 62a of the mesh screen 61 may be occluded by the distalends of the light conducting members 51. In some cases an additionallight transparent very thin layer may be deposited across the screen 61to prevent the loss of luminescent material.

Instead of two mesh screens 60 and 61 a perforated plate 65 of a metalor of an opaque material such as plastic may be used to form aluminescent screen 68 as shown in FIG. 4C. The plate 65 has straight ortapered channels 66 extending across the entire thickness of said platewhich can accomodate and hold the light conducting members 51 and inaddition provide open spaces 67 on each side of said members 51 fordepositing luminescent material 54a therein. The luminescent material54a may be injected in liquid form such as a solution of NaI(Tl) or in apowdered form or in a crystal form as it was explained above.

Another modification of this invention is shown in FIG. 4D, which showsa perforated honey-comb 40 used instead of a perforated plate 65described above. It was found that honeycomb 40 permits easyconstruction of long channels 41 which are necessary for luminescentlayers. The honey-comb support for light conducting members 51 may havechannels 41 of tapered configuration or of parallel configuration. Thechannels 41 may be open at both ends or may be closed at one or bothends. The sidewalls of honeycomb are preferably light opaque'and lightreflecting. A great advantage of this novel construction resides in thefacility of depositing luminescent material in the necessary thicknesson sidewalls of each of plurality of light conducting members 51 andrepresents therefore an important feature of this invention.

Another embodiment of this invention is shown in FIG. 4E whichillustrates the luminescent screen 70. In this embodiment the conicallight conducting members 51 are leached out to provide empty spaces 71or even passages therein forming thereby hollow light conducting members51A. The empty spaces 71 may extend through the entire length of members51A or may terminate before their endfaces 51a. The hollow spaces 71should not extend laterally to the external part of the light conductingmembers which is of a lower index of refraction 53 but should beconfined by the residual wall of material of high index of refraction52. In this embodiment light opaque means should be provided between thetwo adjacent members 51A or at least between the pairs of two adjacentmembers 51A to prevent optical cross-talk by luminescent radiationescaping through sidewalls of said members 51A.

FIG. 4F illustrates another modification showing the luminescent screen80 in which light conducting members 51A are mounted in a metal orplastic plate 82 which has straight or tapered passages for acceptingthe conical and hollow light conducting members 51A and for providingspaces 71 for deposition of the luminescent material 54, as it wasdescribed above and shown in FIG. 4E.

Instead of a perforated plate 82, mesh screens 61 and 62 can be used atthe ends of light conducting members 51A, as it was described above andillustrated in FIG. 4D.

It should be understood that each of the opposite ends of the conicallight conducting members may be mounted inside the mesh screens or 61 orperforated plate 65 or perforated honeycomb or crate-like supportingmember or may be mounted flush with the openings of said mesh screens 60or 61 or with openings of said plate 65 or of said honey-comb or may bemounted outside of said openings of said mesh screens or of said plateor of said honeycomb supporting member.

It should be understood that each of luminescent screens described mayhave an additional layer of luminescent material deposited on its inputendface as it is shown in FIG. 4A for layer 58.

It should be understood that in all luminescent screens described theinput endface 51b of light conducting members 51 or 51A or theirmodifications may be made larger than the output endface 51a of saidmembers. It was found however that in this construction a much largerpercentage of luminescent light escapes through the sidewalls of lightconducting members.

It should be understood that each of luminescent screens described maybe mounted in a spaced relationship to the vacuum tube 2 or itsmodifications or may be mounted in contact with the input endwall 6 orits modifications. In some cases it is preferably to use the luminescentscreens described herein as part of the input endwall 6 or itsmodifications of the vacuum tube 2 or its modifications. Thisconstruction was found to improve the sensitivity of the camera. In thisembodiment an additional light transparent layer of glass 'or potassiumsilicate may be added to the end-face of the luminescent screen toimprove vacuum-tightness of said insert.

It should be understood that each of novel luminescent screens describedmay be mounted inside the vacuum tube 2. In such case the photocathode 7of tube 2 is mounted on the outside endfaces 51a of said luminescentscreen and may be in contact with said endface or may be separated fromsaid endface by A10 or of silicon oxide or of light transparent heatresistant plastics such as described above. It should be understood thatall modifications of the mounting and supporting of the luminescentscreen 3 described above apply as well to the novel luminescent screens50, 63, or and their modifications.

It should be understood that all novel luminescent screens 50, 63, 70and 80 and their modifications may be used also for X-ray ImageIntensifiers and Neutron Image Intensifiers. If the X-ray ImageIntensifiers are used for medical diagnosis in which the energy of X-rays does not exceed -140 KV, the phosphor layers 54a and 54b may be ofa smaller length than in Radio- Isotope Cameras. The embodiment of suchX-ray or neutron image intensifier shown in FIG. 4F; in which the novelfiberoptic luminescent screens serve in addition as a support for thephotocathode 7.

In the use in neutron image intensifiers, the phosphor layers 54a and54b may be enriched with materials which capture neutrons such as boron,indium, cadmium, gadolinium or hydrogenous compounds such as paraffin.The neutron captivating materials may be also provided in the form of aseparate layer adjacent to the phosphor layers 54a and 54b.

It should be understood that the novel luminescent screens alone ortogether with image intensifiers described above can be used forproducing neutron images by a transfer technique which is described inthe book titled Neutron Radiography by H. Berger.

It should be understood that all novel luminescent screens 50, 63, 70,80 or their modifications may be used with all vacuum tubes describedabove instead of the luminescent screen 3 or in addition to saidluminescent screen 3.

It should be understood that in some cases the light conducting members51 may have parallel sidewalls or other configuration instead of thetapered shape described above and that such construction applies to allembodiments of invention.

In conclusion it was found that in many radio-isotope examinations, theuse of novel luminescent screens described above was essential for theoperation of the entire imaging camera devices.

In addition it should be understood that all vacuum tubes describedabove may be provided'with image intensifying plates 36 of channelledelectron multiplier type, shown in FIG. 3.

It should be understood that all novel luminescent screens and theirmodifications may be used in some applications with an array ofsolid-state photosensors instead of using vacuum tubes described above.The photosensors may be photo-cells such as of CdS or photo-diodesespecially of avalanche type, p-i-n detectors or phototransistors.

It should be understood that all the novel luminescent screens describedherein and their modifications may be used in X-ray Cassettes as imageintensifying screens instead of standard intensifying screens as it isshown in FIG. 46.

All novel luminescent screens can be also used in combination with solidstate intensifiers such as panels comprising photoconductive layers andelectroluminescent layers, described e.g. in the book OptoelectronicDevices" by Weber.

As various possible embodiments might be made of the above invention,and as various changes might be made in the embodiments above set forth,it is to be understood that all matter herein set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

What I claim is:

1. A camera for examination of internal parts of the body formed byradio-isotopes emitting an invisible radiation comprising in combinationluminescent means producing a first luminescent light pattern, vacuumtube means provided with a photoelectric screen mounted within saidtube, said vacuum tube means converting said first pattern into a secondluminescent pattern, a television pick-up tube for receiving said secondluminescent pattern and converting said second pattern into an electronbeam, a scanning aperture mounted in the path of said electron beam andmeans for deflecting said electron beam across said aperture, and meansconverting the electrons of said beam transmitted through said apertureinto successive electrical signals, said device comprising furthermoremeans for receiving said signals and discriminating said signals wherebyonly signals of a predetermined amplitude are passed ,and means forreceiving said passed signals and utilizing said signals.

2. A device as defined in claim 1, in which said television tube isprovided with an endwall having at least a part constituted of aplurality of light conducting members comprising a core of a transparentmaterial of a high index of refraction, and a peripheral part ofmaterial of a lower index of refraction than said core, said membersconducting light by internal reflection.

3. A device as defined in claim 1, in which said luminescent meanscomprise a plurality of light conducting members and a luminescentmaterial mounted along the sidewalls of said light conducting members Iand outside of said light conducting members, and in which thelongitudinal dimension of said luminescent material if greater than thetransverse dimension, in which device furthermore said membersconducting light by internal reflection.

4. A device as defined in claim 3, in which said light conductingmembers have an internal part of a transparent material of a high indexof refraction and an external part of material of a lower index ofrefraction than said internal part.

5. A device as defined in claim 3, in which said light conductingmembers and said luminescent means are mounted in channels of asupporting member.

6. A device comprising in combination a luminescent array comprising aplurality of light conducting members comprising a light transparentmaterial and phosphor means mounted along the sidewalls of said lightconducting members and emitting luminescent light in response to aninvisible radiation, said phosphor means having the longitudinaldimension greater than their transverse dimension, and means forreceiving and utilizing said luminescent light.

7. A device as defined in claim 6, in which said light conductingmembers have a conical shape.

8. A device as defined in claim 6, in which the external part of saidlight conducting members comprises material of a lower index ofrefraction than the internal part of said light conducting members, andin which device said members conduct said luminescent light by internalreflection.

9. A device as defined in claim 8 in which said phosphor means aresupported by said sidewalls.

10. A device as defined in claim 9 in which said light conductingmembers are united together and in which said receiving means comprise avacuum tube.

11. A device as defined in claim 8 in which light opaque means aremounted between said phosphor means.

12. A device as defined in claim 7 in which said light conductingmembers are united together to form a screen.

13. A device as defined in claim 7 in which light opaque means aremounted between said phosphor means, and in which the external part ofsaid members comprises material of a lower index of refraction than theinternal part of said members.

1. A camera for examination of internal parts of the body formed byradio-isotopes emitting an invisible radiation comprising in combinationluminescent means producing a first luminescent light pattern, vacuumtube means provided with a photoelectric screen mounted within saidtube, said vacuum tube means converting said first pattern into a secondluminescent pattern, a television pick-up tube for receiving said secondluminescent pattern and converting said second pattern into an electronbeam, a scanning aperture mounted in the path of said electron beam andmeans for deflecting said electron beam across said aperture, and meansconverting the electrons of said beam transmitted through said apertureinto successive electrical signals, said device comprising furthermoremeans for receiving said signals and discriminating said signals wherebyonly signals of a predetermined amplitude are passed ,and means forreceiving said passed signals and utilizing said signals.
 2. A device asdefined in claim 1, in which said television tube is provided with anendwall having at least a part constituted of a plurality of lightconducting members comprising a core of a transparent material of a highindex of refraction, and a peripheral part of material of a lower indexof refraction than said core, said members conducting light by internalreflection.
 3. A device as defined in claim 1, in which said luminescentmeans comprise a plurality of light conducting members and a luminescentmaterial mounted along the sidewalls of said light conducting membersand outside of said light conducting members, and in which thelongitudinal dimension of said luminescent material if greater than thetransverse dimension, in which device furthermore said membersconducting light by internal reflection.
 4. A device as defined in claim3, in which said light conducting members have an internal part of atransparent material of a high index of refraction and an external partof material of a lower index of refraction than said internal part.
 5. Adevice as defined in claim 3, in which said light conducting members Andsaid luminescent means are mounted in channels of a supporting member.6. A device comprising in combination a luminescent array comprising aplurality of light conducting members comprising a light transparentmaterial and phosphor means mounted along the sidewalls of said lightconducting members and emitting luminescent light in response to aninvisible radiation, said phosphor means having the longitudinaldimension greater than their transverse dimension, and means forreceiving and utilizing said luminescent light.
 7. A device as definedin claim 6, in which said light conducting members have a conical shape.8. A device as defined in claim 6, in which the external part of saidlight conducting members comprises material of a lower index ofrefraction than the internal part of said light conducting members, andin which device said members conduct said luminescent light by internalreflection.
 9. A device as defined in claim 8 in which said phosphormeans are supported by said sidewalls.
 10. A device as defined in claim9 in which said light conducting members are united together and inwhich said receiving means comprise a vacuum tube.
 11. A device asdefined in claim 8 in which light opaque means are mounted between saidphosphor means.
 12. A device as defined in claim 7 in which said lightconducting members are united together to form a screen.